Caffeic acid phenols

FIG. 2 Major caffeic acid phenols (CAP) found in Echinacea. 

Unsaturated lipophilic compounds, caffeic acid phenols (CAP) and polysaccharides are believed to be responsible for the observed immunos-timulatory activity. The alkamides and ketoalkenes/alkynes (Figure 1) are the two major groups in the unsaturated lipophilic compound category. 

AVERAGE TOTAL CAFFEIC ACID PHENOL CONTENT (mg/g DRY ROOT) OF VARIOUS ECHINACEA SPECIES AND VARIETIES GROWN UNDER CULTIVATED AND WILD ENVIRONMENTS 1... 

Nutrient availability also plays a major role in exudation, with deficiencies in N, P, or K often increasing the rate of exudation (218). It is believed that nutrient deficiency may trigger the release of substances such as organic acids or nonproteinogenic amino acids (phytosiderophores), which may enhance the acquisition of the limiting nutrient (219,220). An example here might be the release of phenolic acids such as caffeic acid in response to iron deficiency, which results in an increase in uptake of the cation (221). 

Morreel, K. Ralph, J. Lu, F Goeminne, G. Busson, R. Herdewijn, P. Goeman, J. L. Van der Eycken, J. Boeijan, W. Messens, E. Phenolic profiling of caffeic acid O-methyltransferase-dehcient poplar reveals novel benzodioxane oligolignols. Plant Physiol. 2004, 136, 4023 1036. 

Another phenolic compound, caffeic acid, altered the mineral content of Argyrodendron trlfoliolatum after 6 months (25). Zn2+,... 

Chlorogenic acid loss is also correlated with its incorporation in browning products.3 During roasting, the diphenols, 4-ethylpyrocatechol and pyrocatechol are formed from the caffeic acid moiety and the quinic acid moiety yields phenol and benzoic acid as well as all the di- and trihydroxybenzenes.39... 

How the aliphatic monomers are incorporated into the suberin polymer is not known. Presumably, activated co-hydroxy acids and dicarboxylic acids are ester-ified to the hydroxyl groups as found in cutin biosynthesis. The long chain fatty alcohols might be incorporated into suberin via esterification with phenylpro-panoic acids such as ferulic acid, followed by peroxidase-catalyzed polymerization of the phenolic derivative. This suggestion is based on the finding that ferulic acid esters of very long chain fatty alcohols are frequently found in sub-erin-associated waxes. The recently cloned hydroxycinnamoyl-CoA tyramine N-(hydroxycinnamoyl) transferase [77] may produce a tyramide derivative of the phenolic compound that may then be incorporated into the polymer by a peroxidase. The glycerol triester composed of a fatty acid, caffeic acid and a>-hydroxy acid found in the suberin associated wax [40] may also be incorporated into the polymer by a peroxidase. 

Simple phenolic compounds include (1) the phenylpropanoids, trans-cinnamic acid, p-coumaric acid and their derivatives (2) the phenylpropanoid lactones called coumarins (Fig. 3.4) and (3) benzoic acid derivatives in which two carbons have been cleaved from the three carbon side chain (Fig. 3.2). More complex molecules are elaborated by additions to these basic carbon skeletons. For example, the addition of quinic acid to caffeic acid produces chlorogenic acid, which accumulates in cut lettuce and contributes to tissue browning (Fig. 3.5). 

Wang et al. (62) reported the oxidative polymerization of a mixture of phenolic compounds in aqueous solution containing mont-morillonlte, illite, and kaolinite, each of which had been mixed with quartz in a 3 7 ratio, and by quartz alone. The mixture of phenolic compounds contained gallic acid, pyrogallol, protocatechuic acid, caffeic acid, orcinol, ferulic acid, p-coumaric acid, syringic acid, vanillic acid, and p-hydroxybenzoic acid. The oxidative... 

Phenolic acid A = ferulic acid phenolic acid B = caffeic acid flavonoid A = isoquercitrin flavonoid B = hyperoside phenolic acid E = chlorogenic acid flavonoid C = rutin. 

Simple phenolics Phloroglucinol, gentisic acid, vanillin, caffeic acid, ferulic acid... 

By this method, we found the symbionts could utilize (and apparently detoxify) a diversity of plant flavonoids and phenolics including rutin, quercetin, caffeic acid, tannic acid, and gallic acid (11),... 

Figure 6. Separation of free phenolic acids. 1, Caffeic acid 2, p-coumaric acid 3, sinapic acid. Column 18 cm x 0.22 mm I.D. 3-um Spherisorb ODS. Mobile phase methanol-water-acetic acid (20 75 5). Detection TIC (ions of m/z <60 suppressed). Ion source temperature 210 C.

Correlation Between Total Phenols Expressed as Percent Caffeic Acid Equivalents and Ozone Injury. Twelve cultivars of peanuts ranging from low to high ozone sensitivity were examined. Foliage of each of the cultivars was evaluated for content of total phenols before and after ozone treatment. Because of the relatively high concentrations of caffeic acid in peanut foliage, values are expressed as percent caffeic equivalents in the total phenol assay. Experimental results used in establishing the correlation between caffeic acid and ozone injury are shown in Table I. 

Table I. Index of ozone injury to foliage of 12 peanut cultivars and total plant phenol expresses "a % caffeic acid equivalents in assay...

Total plant phenol expresses as % caffeic acid equivalents in assay... 

Plant susceptibility to ozone as determined by visible injury may be very closely related to quantities of o-diphenols associated with the chloroplasts and specific requirements for activation of polyphenol oxidase enzymes. There is a significant correlation between ozone injury and concentrations of total phenols expressed as percent caffeic acid equivalents in peanut cultivars. This concept is not intended to underestimate the importance of membranes that separate phenols and enzymes. Perhaps future research will demonstrate that membranes of resistant alfalfa, green bean and other species differ both qualitatively and quantitatively from those of susceptible plants of these species. 

Phenolic acids Benzoic acid derivatives OH Caffeic acid 1 Gentisic acid Benzoic acid 1 1 Vanllic acid Protocatechuic acid 1 /7-Hydroxybenzoic acid COOH Syringic acid Hydroxy-isochromans HO. l-phenyh6,7- dihydroxy-isochroman l-(3 -methoxy-4- hydroxyphenyh6,7- dihydroxydsochroman R1... 

Rechner, A.R., Pannala, A.S., and Rice-Evans, C.A., Caffeic acid derivatives in artichoke extract are metabolised to phenolic acids in vivo. Free Radical Res., 35, 195, 2001. 

Phenylpropanes are aromatic compounds with a propyl side chain attached to the benzene ring, which can be derived directly from phenylalanine. Naturally occurring phenylpropanoids often contain oxygenated substituents, e.g. OH, OMe or methylenedioxy, on the benzene ring. Phenylpropanoids with hydroxyl substituent(s) on the benzene ring belongs to the group of phenolics, e.g. caffeic acid and coumaric acid. 

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